I am so sorry you are having this trouble with your eggs. I know how it feels. Last year, I had well over twenty call duck eggs under broody hens. Straight forward fact: call ducks are extremely challenging to hatch. It is not your fault at all 

 I had multiple eggs just quit along the way, and by the time lock down came, I was left with one egg. I waited, candled, looked for a pip. Nothing. I believe it was around day thirty when I took action. The duckling was miraculously alive, but the entire hatching process had to be carefully completed by me. Becuase call ducks have such short bills, it is harder for them to pip. And this poor baby was exhausted from trying. For a while, I wasn’t sure it was going to make it, but after resting for a full forty-eight hours, things began to progress, and Willow is now a beautiful little call duck hen. Good luck!